Matrix had a good first part... Part 2 was somewhat decent, and with part 3 I was more or less like: are they even trying?

MIB kind of the same.

X-Men could've been decent if I could really remember all that much about it. I guess they mostly suffered from the latter bits and pieces where continueity went out the window and the movies just did whatever.

And while BTTF has quite a few plotholes and gaps, personally I've found I wouldn't mind rewatching that one now and again. And it remains fun to watch to me.

I don't care for any of these trilogies, really. The best scifi is still locked up in book form and it's likely to be made into TV series instead of movies.

That I certainly agree with.

If they ever make Iain M Bank's culture novels in to a series I'll be getting the box set !

YESSSSS!!! Me, too! I love the Culture series. Each book needs to be at least a good, long season. I think the eaters from Consider Phlebas would need at least 2 long episodes to drive home how truly effed up they are.

I thought the first Matrix topped everything on this list. It was novel in concept, breakthrough on effects, and had all the parts for an incredible universe. Then came the sequels and they ruined it. If it weren't for that, I'd have picked it, but had to go with X-Men as my next choice. I really like MiB, too, and can't wait for the fourth - but mostly because it's funny Sci-Fi.

I went with Back to the Future. That is based more on my childhood self seeing them in the theater than my opinion now, although I would probably watch them a dozen times before watching the other choices.

The Matrix trilogy could have been something special if they had managed to capture even half of the magic of the first film in the other two. If you splice in the video cut scenes from the Enter the Matrix video game (which was filmed at the same time as 2 & 3) it really helps the second movie out. Nothing can help that third movie however.

MIB Trilogy? They made a third movie? Huh... I gave up after the train-wreck that was the second one.

The Xmen Trilogy... Once again the series started out strong (by the standards of the day) and fell apart quickly. I did see the third one but it was so bad I nearly forgot I had even seen the second one let alone that the third one existed.

How such a topic is made without the original Star Wars trilogy listed is beyond me.

I had to vote for MIB because it was the only trilogy to have more than one good entry IMO. The Matrix and BttF both had stronger first entries, but both the first and second MIB movies were good and MIB3 was still ok, whereas the second and third Matrix movies were just a giant dumpster fire and BttF two and three were forgettable at best. And all the X-Men movies were just overwhelmingly "meh" so I can't consider them the best of anything in any sense.

Back to the Future is the best. There is no mistake that the original Matrix movie was awesome, but it fell flat on the two sequels. As did Men in Black and X-men. Back to the Future is imho the trilogy that each movie was pretty close to equal. The first one is the best and its sequels do not drag down the original like the other trilogies in this list.